A locking system has a lock housing having first pin slots, a lock cylinder having second pin slots and being supported within the lock housing such that rotation of the lock cylinder is dependent upon a position of tumbler pins within the pin slots, and an idler block defining a keyway to receive a deviated key in which the idler block is rotatable relative to the lock cylinder between an entry position and a pin position aligning the key with the pin slots. One or more translating shields in the idler block are movable from an open position in which the keyway is unobstructed by the shield to allow for insertion or removal of the deviated key and a closed position in which the translating shield protrudes at least partway into a path of the keyway without interfering with rotation of the deviated key with the idler block.